The effect of microwave radiation on physico-chemical properties and in vitro digestibility of barley straw

Abstract

The effects of microwave radiation on chemical properties and in vitro digestibility of barley straw were investigated. Barley straw (90% dry matter, DM) was separated manually into stem, leaf and leaf sheath. Only the stem component was the subject of the study. The stem samples were cut into 5 cm long segments before exposing to one of 5 different times of microwave radiation (MWR), 1.5 kw, 2450 MHz: T0 = control (without MWR), T1 = MWR for 1 minute, T2 = MWR for 2 minutes, T3 = MWR for 3 minutes, and T4 = MWR for 4 minutes. Following the treatment, the samples were ground to pass a 1-mm screen before analyzing for chemical properties: dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, hemicellulose, and acid detergent lignin (ADL); and in vitro digestibilities of dry matter (IVDMD) and organic matter (IVOMD). In addition, metabolizable energy (MJ/kg feed dry matter, M/D) of the samples was estimated from IVDMD using theformula provided by SCA (l990). Data analysis indicated that MWR affected the samples in three patterns: DM, NDF, and cellulose were not affected by MWR (P>0.05). OM, ADF, and hemicellulose were affected (P<0.05) by the treatment, but the effects did not follow any pattern related to time of exposure. CP, IVDMD, IVOMD, and M/D increased linearly (P<0.05) as the time of MWR increased from 0 to 4 minutes, the increases by 38%, 12%, 9%, and 13%, respectively. ADL decreased (P<0.067) by 23% as the time of exposure to MWR increased. This study indicated that application of MWR up to 4 minutes significantly increased the nutritive values of barley straw in terms of improved in vitro digestibility and metabolizable energy while lignin content which is recognized as one of antinutrients in most roughages decreased significantly.